1. Field of the Invention
The present invention is directed to new 2-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]vinyl alkanoates, their preparation and their use as intermediates in the preparation of certain synthetic pyrethroids.
2. Summary of the Invention
The present invention is directed to 2-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]vinyl alkanoates having the formula I ##STR1## wherein each Hal independently is a chlorine, fluorine or bromine atom, R is an alkyl group containing from 1 to 5 carbon atoms. The acetate, wherein Hal is chlorine and R in the formula is methyl, is preferred. The alkanoates may be used as an intermediate in the preparation of pyrethroid esters of 2-(2,2-dihalovinyl)-3,3-dimethylcyclopropanecarboxylic acid. The alkanoates according to the invention have two asymmetric carbon atoms in the cyclopropane ring and, therefore may have the (1R,cis), (1R,trans), (1S,cis) or (1S,trans) configuration. The nomenclature used herein to describe the spatial configurations have been defined by M. Elliott et al. in Nature, 248 (1974), 710-711. Among the four spatial configurations of the said alkanoates the (1R,cis) configuration is preferred, because among these four spatial configurations of the pyrethroid esters of 2-(2,2-dihalovinyl)-3,3-dimethylcyclopropanecarboxylic acid the esters with the (1R,cis) configuration have the highest pesticidal activity.
The invention also provides a process for the preparation of 2-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]vinyl alkanoates wherein each halo independently is chloro, fluoro or bromo which comprises reacting 2-(2,2-dihalovinyl-3,3-dimethylcyclopropyl)ethanal with the appropriate anhydride of an alkanoic acid.
The process is suitably carried out in the presence of an amine, preferably a trialkylamine containing from 2-6 carbon atoms in each alkyl group. Starting from the (1R,cis) isomer of 2-(2,2-dimethylcyclopropyl)ethanal, the process of the invention affords 2-(2,2-dimethylcyclopropyl)vinyl alkanoates exclusively in the (1R,cis) configuration.
According to another aspect of the invention, 2-(2,2-dihalovinyl)-3,3-dimethylcyclopropanecarboxylic acid is prepared by ozonolysis of a 2-(2,2-dihalovinyl-3,3-dimethylcyclopropyl)vinyl alkanoate followed by oxidative decomposition of the peroxidic ozonolysis product obtained. Ozonolysis of organic compounds and oxidative decomposition of the peroxidic ozonlysis product obtained is described in, for example, Chemical Reviews 53 (1958), 925-995. The oxidative decomposition may be carried out in the presence of hydrogen peroxide or a per acid, and, if desired, in the presence of a base, for example an alkali metal hydroxide. The presence of a base will yield a salt of 2-(2,2-dihalovinyl)-3,3-dimethylcyclopropanecarboxylic acid; this salt can be converted into the free acid by acidification procedures well known in the art.
The 2-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]ethanal starting material for the present process is prepared from 2-(2,2-dimethoxyethyl)-3,3-dimethylcyclopropanecarbaldehyde, which is prepared as described in U.S. patent application Ser. No. 965,951, filed Dec. 4, 1978, the pertinent disclosures of which are incorporated herein by references, or from 4-hydroxy-2-carene by ozonolysis followed by reduction of the resulting product, both in the presence of an alkanol, to yield 4-acetyl-2-alkoxy-7,7-dimethyl-3-oxabicyclo[4.1.0]heptanes. The 2-methoxy compound is the preferred pyrethroid intermediate and is hydrolyzed with aqueous acid to yield 2-(2-hydroxy-3-oxobutyl)-3,3-dimethylcyclopropanecarbaldehyde which is readily converted to 1-(2-formyl-3,3-dimethylcyclopropyl)-3-oxo-2-butyl acetate by treatment with, e.g., acetyl halide. This acetate is then added to the product of the reaction of a tri(dialkylamino)phosphine or an alkyl ester of an ortho phosphorous acid bis(dialkylamide) with a compound generating a dihalocarbene to yield 1-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]-3-oxo-2-butyl acetate. Oxidation of this compound, e.g., with peroxy acid, yields 2-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]ethylidene diacetate. These reactions are described in the concurrently filed U.S. patent application No. 55,854.
The ethylidene diacetate is readily hydrolyzed, e.g., in the presence of acid, to yield 2-[2-(2,2-dihalovinyl)-3,3-dimethylcyclopropyl]-ethanal as described in the concurrently filed U.S. patent application Ser. No. 55,855, U.S. Pat. No. 4,222,964.